John B. Pendry

Bio: John B. Pendry is an academic researcher from Imperial College London. The author has contributed to research in topics: Metamaterial & Plasmon. The author has an hindex of 100, co-authored 536 publications receiving 88802 citations. Previous affiliations of John B. Pendry include University of California, San Diego & Duke University.

Bonding at surfaces

Abstract: Surface crystallography is a rapidly growing subject in terms of both its scope and capabilities. Some surface structures are examined in detail and their interesting features stressed. We go on to examine new developments in the field, and conclude with a review of possibilities for studying thermal motion at surfaces of both harmonic and anharmonic nature, and of thermal diffusion across the surface.

Mimicking a negative refractive slab by combining two phase conjugators

Abstract: A new route toward a lossless superlens has been proposed recently. It relies on the association of two phase-conjugating sheets. The aim of this study is to show how such a lens can be implemented experimentally at optical frequencies. Because efficient phase conjugation of evanescent waves is illusory with the current technology, only the case of propagating waves is considered here. Four wave mixing in BaTiO3 is shown to provide efficient backward and forward phase conjugation over a major part of the angular spectrum, taking advantage of internal reflections inside the non-linear slab. However, phase distortions arise for high spatial frequencies and limit the resolving power of the device. The addition of a second phase-conjugator automatically compensates for these phase distortions. The wave field is then perfectly translated through the system. Actually, such a device performs even better than a negative refracting lens since the association of two phase-conjugating mirrors behaves like a resonant cavity. An amplification of the wave field by a factor of 102 in intensity is predicted, despite the important absorption in BaTiO3.

Electronic properties of disordered materials: a symmetric group approach

Abstract: The presence of disorder in a solid invalidates most of the methods developed for computing electronic properties. There is a need for a theory which does not rely on an ansatz concerning the wavefunctions and which does not present its solution in terms of impossible to perform summations of infinite and sometimes unidentified perturbation series. In an earlier set of papers, the authors have shown how the transfer matrix method can be generalised in the one-dimensional (1D) case to treat the case of a disordered solid, enabling densities of states and mean inverse localisation lengths to be calculated. This was done by application of the symmetric group to direct products of transfer matrices. Here the authors consider the case of arbitrary dimensions and show that, whereas the completely symmetric representation sufficed to solve the problem in 1D, in higher dimensions a more extended application of group theory is required. They derive an expression for the density of states in a secular-equation-like form involving diagonalising an infinite matrix which can in practice be truncated to finite dimensions. In the limit of an infinite matrix the theory is exact, and comparisons of calculations made using their theory with simulations for finite systems show that the authors can obtain highly accurate results with a minimum of computational effort.

Multilayer imaging device with negativer permittivity or negative permeability layers

Abstract: An imaging device arranged to image near field as well as far field components form an object comprises a stack of layers (8) spaced apart from each other, the layers having a negative real part of electrical permittivity or magnetic permeability in a direction normal to the layers, and being constructed from microstructured material comprising an array of elements spaced apart from each other by a distance less than the wavelength of radiation to be imaged. The layers may be spaced by medium of positive real part of electrical permittivity or magnetic permeability, both the layer and the spacing being isotropic. In an alternative embodiment, the layers are in pairs in which the component of electrical permittivity or magnetic permeability in a direction normal to the layers is alternately negative and positive, while the electrical permittivity or magnetic permeability in a transverse direction is positive or negative, respectively. In an alternative embodiment, the magnitude of the component of the electrical permittivity or magnetic permeability is very large in a direction normal to the incident face.

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

Surface plasmon subwavelength optics

Abstract: Surface plasmons are waves that propagate along the surface of a conductor. By altering the structure of a metal's surface, the properties of surface plasmons--in particular their interaction with light--can be tailored, which offers the potential for developing new types of photonic device. This could lead to miniaturized photonic circuits with length scales that are much smaller than those currently achieved. Surface plasmons are being explored for their potential in subwavelength optics, data storage, light generation, microscopy and bio-photonics.

Experimental Verification of a Negative Index of Refraction

Abstract: We present experimental scattering data at microwave frequencies on a structured metamaterial that exhibits a frequency band where the effective index of refraction (n) is negative. The material consists of a two-dimensional array of repeated unit cells of copper strips and split ring resonators on interlocking strips of standard circuit board material. By measuring the scattering angle of the transmitted beam through a prism fabricated from this material, we determine the effective n, appropriate to Snell's law. These experiments directly confirm the predictions of Maxwell's equations that n is given by the negative square root of epsilon.mu for the frequencies where both the permittivity (epsilon) and the permeability (mu) are negative. Configurations of geometrical optical designs are now possible that could not be realized by positive index materials.

Magnetism from conductors and enhanced nonlinear phenomena

Abstract: We show that microstructures built from nonmagnetic conducting sheets exhibit an effective magnetic permeability /spl mu//sub eff/, which can be tuned to values not accessible in naturally occurring materials, including large imaginary components of /spl mu//sub eff/. The microstructure is on a scale much less than the wavelength of radiation, is not resolved by incident microwaves, and uses a very low density of metal so that structures can be extremely lightweight. Most of the structures are resonant due to internal capacitance and inductance, and resonant enhancement combined with compression of electrical energy into a very small volume greatly enhances the energy density at critical locations in the structure, easily by factors of a million and possibly by much more. Weakly nonlinear materials placed at these critical locations will show greatly enhanced effects raising the possibility of manufacturing active structures whose properties can be switched at will between many states.

Plasmonics for improved photovoltaic devices

Abstract: The emerging field of plasmonics has yielded methods for guiding and localizing light at the nanoscale, well below the scale of the wavelength of light in free space. Now plasmonics researchers are turning their attention to photovoltaics, where design approaches based on plasmonics can be used to improve absorption in photovoltaic devices, permitting a considerable reduction in the physical thickness of solar photovoltaic absorber layers, and yielding new options for solar-cell design. In this review, we survey recent advances at the intersection of plasmonics and photovoltaics and offer an outlook on the future of solar cells based on these principles.